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thanks for the response tenaja, all looks interesting. The handheld Velleman is nice. I will probably use it for automotive stuff as well so the portability would be outstanding. I do own an Asus...

I was looking at getting my first o-scope, I have used a few at work, and at school.

PC o-scope just sounds attractive to me.

Other than that what are some good choices? Or what should I look...

I have recently seen most of the set backs using PBP, its a great program and everything, just a little limited for me.

So I have been learning C, fairly simple, easy concepts etc...

Just...

I updated the spreadsheet, feel free to take a look

www.drivearu.com/Electronics/ntc%20thermistor.xls

I am pretty confidant in this one, no exponents which is nice, and I looked at other...

interesting, I have heard about the capacitor trick. How would it be done "averaging" in software?

I am going to use an op amp to get me full range of my 0-5v scale instead of this 0-1v stuff... would that limit the signal from "bouncing" around?

So I looked at the resistor that was used, its 510

It brings the change in resistance per degree down to
3 ohm from 100-150
2 ohm from 151-200
1 ohm from 201-250

Isnt that crazy.

Wow, you mention that and I look at the gauge that the sender was supposed to work with and they did that!

well, I changed it up and am using three diff power curves to keep everything within 1 degree +/-

only thing that is trouble is negative exponents.. tryin to figure out how to simplify it out so...

f(x) = 5167.68(0.98^x)

It all works, just wondering how I will try to make exponents happen..

Thank you very much!

Wow, that was really easy!

I lost accuracy but its in the place I don't care about!

Ah, forgot that it needs to be the temperature range 100-250 degrees F

When o I get the ability to edit my posts?

I need to figure out how to convert the non-linear AD Value to something more linear as far as the conversion goes.

I figured out by reading a little on NTC thermistors, with the little data I...

What if I switched the VRef+ and Vref- to

Vref+ = 0v
Vref- = 5v

Would that work?

reason why I am not using the 8bit adc is because I would have to use a lot more current to get it up out of the 19mV range, and not really wanting to do that since it seems to vary more, its...

yes, its an autometer 2242 pressure sender unit. its really annoying.

all I have is
15 ohms = 100psi
175 ohms = 10psi


What I am doing right now is using regulated current. ~5mA

didnt work very well... lost again :(

So then I thought it out a little more, and instead of converting to voltage etc.. ADVal represents that value...

SO

highest ADVal = 205

205 - whatever the adval is at for the input from the...

AD Res 1024

Lowest voltage = .085v = 100psi = ADVal 18

Highest voltage = .999v = 10psi = ADVal 205

In order to switch everything around all I did differently was subtract my highest voltage...

I have a similar problem, I got everything to work, except translating the math.

My lowest ADVAL is 0 and it's also the HIGHEST pressure.

I saw how the math worked out for him, but I am lost.

okay, I figured why am I using 2 more resistors than I need to. I took your advice changed programming a little and used the internal pullups, check it out.

Okay, made sense about the Transistors. I changed the NPN to PNP because they were seemed better for the job.

I also added 10k pull-down resistors to the emitter-PIC I/O wire.

Thanks for input

schematic .

Interesting Idea, As far as high power wires, this Circuit will be located under the dash, slightly to the left of the steering wheel - about 4" from the fuse box :eek: